Apparatus for manufacture of stereotype dry mats and similar multilayer sheet materials



March 28, 1950 H. c. FRIEL 2,501,716

APPARATUS FOR MANUFACTURE OF STEREO'I'YPE DRY MATS AND SIMILAR MULTILAYER SHEET MATERIALS Filed July 5, 1946 o v 0 O O 0 O O O O 0 O 0 O O 0 O Z WWW Patented 28, 1950 UNITED STATES PATENT OFFICE APPARATUS FOR MANUFACTURE OF STERE- OTYPE DRY MATS AND SIMILAR MULTI- LAYEB SHEET MATERIALS Harold Clement Friel, Hoosick Falls, N. Y.

Application July 5, 1946. Serial No. 681,564

3 Claims. (CI. 9243) My invention will be here described by way of illustration and example, with particular reference to the manufacture of the material known as matrix paper, being the stock for the stereotype dry mats used extensively in the printing arts; but it will be understood that the principles of my invention are applicable in the same or similar degree to the rapid and continuous production of other kindred special-purpose multilayer sheet materials of fibrous texture, for example, certain electrical insulating materials, which, like matrix paper, it has never to the best of my knowledge, been possible to produce satisfactorily by the methods and machinery commonly used in the paper-making art for the continuous high speed manufacture of ordinary multi-layer products such as paper-board, box board and the like.

The stereotype dry mats cut from matrix paper serve as transfer media in the preparation of stereotype printing plates; that is to say, the printing surfaces contained in a type form or pattern are deeply impressed on the surface of the dry mat, the latter thereby becoming the mold for the casting in curved form or otherwise of the stereotype plates having printing surfaces substantially duplicating the type form. The printing qualities of these plates are thus wholly dependent on the molding properties of the dry mat, the latter being required to take a type impression that is faithful, strong and clear, which means, of course, that the mat material must be able under pressure to stretch down and around the individual type characters, in a uniform manner and without impairment either of its surface smoothness or of its structural integrity.

Furthermore, a stereotype dry mat must have the property. after receiving the type impression, of shrinking appreciably with the utmost accuracy and uniformity; it must also be capable of withstanding repeatedly the high temperatures of casting (up to 700 F). It must always give 2 i have sufficient durability and strength to preserve fully the type impression, and yet must be pliable enough to conform itself readily, for casting, to the cylindrical shape required of stereotype plates when prepared for use on high speed cylinder printing presses. Its heat resistance must be very high, to give adequate protection against brittleness and for maintenance of the pliability. At the same time, the dry mat must be free of any roughness, grain or imperfections that, if present, would record themselves on the printing surfaces of the stereotype plates. It is also required that the dry mat be of low insulating capacity, in order to prevent unfavorable crystallization of the plate alloy, which in turn reduces the fidelity of the printing surface; accordingly the dry mats density must be relatively high, to obtain the requisite heat conductivity for quick cooling of the metal on the surface of the cast-for if the metal cools slowly, the cast is apt to show a leaf-like crystalline structure known as flake that invariably shows up in printing. p

The modern stereotype dry mat that fulfills all these and other complex requirements is a smooth moldable, tough and pliable'sheet of uniform thickness and homogeneous construction and composed of'a large number of plies or layers (from 12 to 22 usually) of specially-prepared cellulose fibres; that is to say the wet pulp stock for matrix paper manufacture must invariably undergo an extremely prolonged and severe beating, causing the fibers to become highly hydrated; consequently the stock thus prepared possesses what is known in paper making as excessive slowness," meaning that it does not part readily with its water. It is this slowness" characteristic of the specially-prepared pulp stock always used for matrix paper manufacture which, per= haps more than anything else, has made it imbeen flat failures.

a quick and free release of the cast and it must There are a number of reasons why it has never been possible, on any known paper or paperboard machine of the muti-cylinder type,

to produce satisfactory matrix paper or other special-purpose multi-layer sheet materials that have to be made from excessively slow pulp stock. In the first place, every such multi-cylinder machine heretofore known or proposed depends upon a single long traveling endless felt, common to its several cylinder molds, to receive and collect on the undersurface of its lower course, the several water-laden pulp webs or layers delivered one after the other from said molds; such a long traveling felt cannot sustain, by the tenuous adhesion of the first of such wet pulp webs to its under surface, the very large number of successively-added wet pulp webs that have to be accumulated for matrix paper manufacture. In the second place, even if the large number of ee-accumulated wet pulp webs could be kept from dropping away from the long felt's under surface, the fact that, in such a machine, the removal of much of the water must always await the passage of the numerous combined wet pulp layers through press rolls, is certain to produce serious disturbances of the fiber formation and to cause what is known in paper making as crushes." These disturbances in fiber formation result from the fact that the so-combined wet pulp webs contain an excessive amount of water, due to the need for using a highly hydrated slow" stock in order to secure the aforesaid physical properties that matrix paper must possess; such stock, be- 3 cause of its slowness cannot get rid of as much water as would ordinary stock, at the points of its transfer to the machine's traveling felt; it follows, therefore, that the physical properties of any multi-ply web made from such stock on any known type of multi-cylinder machine must always fall far short of meeting the aforesaid exacting requirements for a satisfactory material for stereotype dry mats.

My invention as hereinafter described, provides methods and means by which for the first time high-quality matrix paper and stereotype dry mats are produced by multi-cylinder machine operation in a wholly continuous manner, in contra-distinction to the cumbersome and laborious batch method of production on a single cylinder or wet" machine, that has heretofore always been required for these products. At the time, my invention at all times substantially preserves, as hereinafter set forth, the particular and precise conditions of water removal, layer amalgamation and the like that prevail in the old single cylinder "wet machine or batch method of manufacture, and that are absolutely essential to the production of multi-layer sheet material of the proper density, fiber arrangement and other physical characteristics to satisfy the aforesaid extremely exacting requirements of stereotype dry mat material. I secure the delivery of matrix paper from the paper-making instrumentalities of my invention, in continuous web form, at a speed that compares favorably with the delivery speeds achieved by ordinary or known types of multicylinder machines in the continuous manufacture of ordinary laminated products, such as paperboard, box board and the like. In consequence of this, the various operations of drying, calendering, coating, moistening and the like to condition the emerging web material (matrix paper) for stereotype dry mat use, can be performed progressively and in a continuous manner on the traveling web itself as it emerges in endless form from the paper-making instrumentalities, thereby securing maximum uniformity of the product at all times, and doing away with all need for the great amount of costly hand labor that has heretofore been required for stereotype dry mat production.

Other and further objects and advantages of my-invention will be made apparent from the following detailed description thereof, taken in connection with the accompanying drawings, in which Figs. 1 and 2 are schematic views, partly in central vertical section, showing apparatus in accordance with my invention for the rapid and continuous production of such stereotype dry mats, Fig. 2 being drawn to a smaller scale than Fig. 1, and being a prolongation or extension of the right hand end of Fig. 1, from the plane of the line X-X in both figures.

Fig. 3 is a larger scale sectional fragmentary view, showing in more refined form than Fig. 1, the optimum water removal conditions obtained by my invention in each of the zones of amalgamation of the successively-added wet pulp layers.

Like reference characters refer to like parts in the different figures.

Up until now, the only successful and satisfactory commercial production of matrix paper (steorotype dry mat material) ever achieved has been on a single cylinder or wet machines, in the following manner:

From such a machine's single cylinder mold, operating in a stock vat supplied with a wet pulp of thoroughly-beaten and highly-hydrated fibres, is progressively couched, onto a endless traveling felt, a thin wet web or layer of such speciallyprepared slow pulp stock. At the point of such felt's passage between a pair of conventional press rolls, this wet pulp layer or web on its upper surface, having parted with much of its water under the squeezing action of the press rolls has become ideally conditioned for strong adhesion to the hard-surfaced upper press roll. By such adhesion and by said'upper rolls rotation is thus obtained the progressive wind-up on said upper rolls circumference of wrap-upon-wrap of the well-dehydrated thin pulp web, each wrap being left just wet enough for its proper consolidation and amalgamation, under the constantly effective compacting action of the press rolls, with the material of the preceding wrap on said upper press roll.

This progressive wind-up on the upper press roll of the properly-conditioned single thickness material is continued until the required number (usually from 12 to 22) of closely-compacted plies or wraps has been accumulated; then the resulting multi-ply lap or sleeve is cut, longitudinally of the roll, and removed therefrom as a rectanguar sheet (about 44" x 54" in size) which, after drying, is cut up into mats (about 20"x 24" in size) that are later calendered, coated, moistened and otherwise conditioned to ready them for delivery to customers. v

The above-described method of making stereotype dry mats in a succession of small separate batches (the only way in which they have been successfully made heretofore) not only imposes a very low production rate, but involves excessively high labor charges, on account of the great amount of handling that is required to be given to the material at all stages of the operation; largely in consequence of this last, the cost of producing stereotype dry mats is at least 5 or 6 times the cost of producing an equivalent weight of ordinary multi-layer fibrous sheet materials, such as paperboard or box board, that can be made in a continuous manner on multi-cylinder machines. My invention, hereinafter described, secures the production of stereotype dry mats (and other multi-layer sheet materials made from excessively "slow" pulp stock) in a continuous manner, so as to compare favorably in cost with multi-layer products made from ordinary pulp stock.

The manufacture of matrix paper in accordance with my invention contemplates, as shown in Fig. 1, the simultaneous and continuous operation of a whole series of conventional stock vat and cylinder mold units, as great at least in number as the number of layers required by the structure of the finished product. Fig. 1 is a diagrammatic representation of, for example, eightsen of such units, arranged in a close order row and designated by the numerals l-l8 inclusive, break in said figure about midway of its length being intended to indicate those several units, not

shown, but corresponding to the numerals 5-H:

inclusive, that intervene between the units numbered d and 86 respectively. Each of the eighteen units includes, as shown, a stock vat supplied with thoroughly-beaten web pulp and containing a cylinder mold 2! with which is associated a conventional couch roll 23. As thus far described, these duplicate units, except for being provided in an unusually large number, are comparable, in general arrangement, to the duplicate cylinder units of any conventional multi-cylinder paper-making machine of the type commonly used for the continuous production in web form, of various ordinary multi-layer products, such as box board, paperboard and the like.

However, my invention differs radically from all previous multi-cylinder machines in its manner and means of collecting and combining in face-to-face relation the individual wet pulp layers a, a formed by th rotary cylinder molds 2!, 2i of the series of duplicate units l-IB. Usually inmulti-cylinder machines, the several wet pulp webs are picked off successively from their respective forming cylinders by a long traveling endless felt which is common to and in contact,

by its lower course or run, with all of the cylinders of the series. In the multi-cylinder machine of my invention, as shown by Fig. 1, each unit of the series has its own individual traveling endless felt 22', which in arrangement and operation is comparable to the traveling endless felt oi the above-described single cylinder or wet" machine. The felt 22 in each of the units I-IB inclusive makes contact with the upper part of the associated cylinder mold 2! and then passes around couch roll 23' and over and around a lower press roll 23', whose rotation by any suitable driving means, not shown, produces said felts movement, which in turn causes rotation of said cylinder mold 2|. Suitably arranged guide rolls 26', 26 are provided to give each felt 22' a return run that carries it past suitable cleansing showers 21 on the way to its cylinder mold 2i.

In each unit 148 inclusive a water-laden web a of the slow stock, deposited continuously on the felts under surface by its cylinder mold is conveyed by said felt to pressing means constituted in part by the associated lower press roll 23', and in each unit the conveyed pulp webv or layer leaves its felt 22' at the place of the latters passage around said lower press roll 24'. All the lower press rolls 2B of the several units are arranged in substantially the same plane; the means directly cooperating therewith, for nip pressure (water removal) pu poses, and for collecting, compacting and properly amalgamat ing the numerous slow pulp webs or layers it delivered by the felts 22', is provided by the lower course or run 30 of an endless conveyor belt 3i, made preferably of stainless steel, or other suitable hard-surfaced smooth water-impervious ma-- terial, which is sufficiently flexible to operate as a belt. The belt 3| is supported at opposite ends of its travel by suitable rotary drums 32 and 32', the former being arranged over the lower press roll 26' of the first unit I and the latter being arranged over the lower press roll 24 of the last unit Id. The belts lower course 30 rests on the several aligned lower press rolls 24 and its upper course may be prevented from sagging unduly by any suitable means, as by spaced supporting rolls The belts lower course 30 at the several points opposite to its contacts with the lower press rolls 2d of units 2-H inclusive is backed up, for pressure-exerting purposes by a series of rolls 33, the latter, together with the end drums 32 and 32, constituting in effect a series of upper press rolls each in co-actin relation to one of the series of lower press rolls 24'; that is to say, for pressure applying purposes each of said rolls 33, as well as each of the drums 32 and 32', is provided with any suitable means, such as springs, weights or pneumatic cylinders, not shown, for applying downward pressure in regulated amount through the belts lower course 30 against any material delivered by the felts 22' over the several rolls 24. This arrangement also obtains movement of belt 3| at the same surface speed as that of the several lower press rolls 24', being a speed which corresponds substantially to the delivery speed imparted to each of the several wet pulp layers a, a by their respective carrying or transfer felts 22.

With the above described apparatus in operation, the wet pulp layer a delivered by the felt 22' of the first unit I is ideally conditioned by the nip pressure of the first pair of press rolls 24', 32 to obtain a very strong adhesion with the smooth under surface of the traveling belt course 30, this initial squeezed-out web or layer, as indicated at 11, being carried forward by the belts lower course through the successive pressing stations constituted by the pairs of press rolls 24', 33 of units 2-" inclusive and by the final press rolls 24', 32' of unit l8. At each such pressing station in succession is delivered from below in the same manner another slow pulp web or layer a from which the excess water is individually squeezed out by the pressing action, to condition it for proper amalgamation by said pressing action with all the squeezed-out webs or layers 1), b, from preceding units that have been collected and consolidated on the under side of the traveling belt course 30. On the latter the collected pulp material gradually increases in thickness as more and more of the units are encountered until the pressing station (roll 24' and drum 32) 'of the last unit is reached; from there the numerous collected webs b, b, emerge contlnuously as a well-integrated multi-layer web 34, of uniform texture, wholly free of crushes and having all the special physica1 properties and characteristics possessed by the multi-layer sheet of limited size that, in the only previously known way of making matrix paper, is accumulated, wrap-upon-wrap, on the upper press roll of a single cylinder or wet" machine, as heretofore described. The reasons for this substantial identity of the two. products (matrix paper made on a single cylinder machine, and matrix paper made on my multi-cylinder machine) are self-evident.

Precisely as the first wrap of pulp material, bereft of its excess water at the press rolls of the single cylinder machine, is ideally conditioned .to adhere strongly to the hard arcuately-moving surface of the upper press roll, so the ntire pulp web b from the first unit I of my machine is similarly bereft of its excess water by effective press roll action (drum 32 acting through belt 3| against roll 24') to thereby obtain an equally stron adhesion to the hard rectilinearly moving under surface of said belts lower course 30. Again, Just as each subsequent wrap of pulp material accumulated on the upper press roll of the single cylinder machine is individually pre-conditioned, by press roll removal of its excess water, for proper face-to-face amalgamation with the pulp material of the preceding wrap about said upper roll, so also is each of any of the pulp webs b, b from subsequent units (2 to l8 inclusive) of my machine, individually pre-conditioned, by press roll removal of its excess water, for proper face-to-face amalgamation, progressively and continuously, with the preceding pulp web b on the under surface of the traveling belt course 30. In short, the above-described continuous production of the multi-layer web 34 by the apparatus of Fig. 1 iscarried out so as to preserve and duplicate in full measure the water-removing and layer-amalgamating and compacting actions, (characteristic of the above-described wind-up of successive squeezed-out wraps of pulp on the single cylinder machines' upper press roll) that are so essential to the production of a satisfactory material (matrix paper) for use in the manufacture of stereotype dry mats.

For the purpose last mentioned, said web 34 as fast as produced by the apparatus of Fig. 1 is adapted to be passed continuously, as shown in Fig. 2, through suitable banks of conventional drier cylinders 35, beyond which are located a set or sets of calendering rolls 38, for operation on the continuous web material 34. The latter is shown next as delivering onto a suitable conveyor 31, by which it is carried past suitable coating apparatus, indicated at 38, and then past suitable moistening apparatus, as indicated at 39, before being delivered to cutting devices shown diagrammatically at 40, which operate on the calendere'd, coated and moistened web to cut it, both transversely and edgewise, to the exact size required for stereotype dry mats.

Fig. 3 illustrates fragmentarily, on a somewhat larger scale than Fig. l, a modification in the travel of each of the several felts 22' by which to secure superior amalgamation between the successive pulp webs b, b as deposited one upon the other, against the under surface of the traveling belt course 30. In this modification, each felt 22' on the way to its associated press roll station 24', 33, is carried over a roll 4| so positioned as to dispose the wet pulp web a, for a short distance before it reaches the press rolls, in virtual contact, without pressure, with the last-deposited pulp web b on the under surface of traveling belt course 30. This arrangement is advantageous in that amalgamation of the webs or layers takes place in the presence of ample water, and also in that it prevents the squeezed-out water at each pressing station from running back along the felt 22' and washing ofi any of the pulp of the wet web or layer a: such squeezed-out water can be readily collected in a conventional catchall 42 here shown as positioned beneath each press roll 24' and the associated preceding supplementary roll I l My invention, as above described, not only has extremely important advantages in materially increasing the production and reducing the cost of stereotype dry mats and other multi-layer sheet materials that have to be made from slow" stock, but it also lends itself to the maximum continuity of operation in the manufacture of such products. Preferably, in the practice of my invention, the number of units (each in effect a wet machine) will be at least one greater than the number of plies or thicknesses required by the finished product; by thus providing an extra normally-idle or inoperative unit, it is possible, upon the breakage or wearing out of any one of the individual felts 22', to continue the full operation of the machine, while such felt is being replaced; the extra unit being always available to supply the pulp material needed to maintain the product at uniform thickness.

Of even greater importance is the fact that my invention produces stereotype dry mats which are much more uniform than those produced by the prior art batch method on a single cylinder or wet machine. It is a recognized fact that in the operation of the said batch method, mats produced when operating with a relatively new transfer felt will be quite different from those that are produced when operating with a transfer felt, which after a couple of hundred hours of use, is approaching the end of its usefulness and is about to be replaced with a new felt. On the other hand, in the apparatus of my invention the felts 22' are so numerous that the replacement of any of them from time to time in the continuous operation of my improved process has little or no effect on the texture thickness and physical properties of the finished mats, the latter at all times being of a quality that reflects the average condition and age of the multiplicity of felts 22.

Another advantage that flows from the multiunit character of my machine is the fact that it permits the use of several grades of raw material at the same time for the different laminations of the product. For example, it is possible and practicable to use a high grade bleached sulphite for the faces of the stereotype mats by supplying such stock, say, to the units numbered [-5 inelusive; unbleached stock of the same grade can be supplied for the back of the mat, say, to the units l4-l8 inclusive; the intermediate units of the series, for the center of the mat, can be supplied with heavily beaten and highly hydrated sulphite stock of somewhat lesser quality and cost without in any way sacrificing any of the physical characteristics which are required in a stereotyping matrix. This same selectivity in also applicable to the use of coloring materials and chemicals, if any are required. In other words, such ingredients (colorings and chemicals) can be supplied only to those units which correspond to the exterior laminations of the mat; since the interior laminations do not need to be colored or chemically treated, there is no need to supply such ingredients to the intermediate units of the series.

While I have described my invention with particular reference to the continuous production of matrix paper and of stereotype dry mats, it will be evident that it is equally applicable to the production of many other products which heretofore have had to be made intermittently in small 76 batches, on wet machines, rather than continuously on multi-cylinder machines, in order to obtain satisfactorily the required physical properties. For example, there are certain types of fibre boards and the like, wherein such properties as hardness, toughness, high density and rigidity are at a premium; in other such multilayer materials the emphasis may be on good bending qualities or moldability. Such properties are obtained for the most part from the kind and treatment of the raw stock and it is well known that the stock for these purposes, so prepared as to give these properties in optimum degree, is, in-most cases, too slow to run satisfactorily on a Fourdrinier machine or on a conventional multi-cylinder machine. My invention, therefore, is particularly applicable to the manufacture of such high grade fibre boards as well as various kinds of press boards, index boards and electrical press boards, used for insulation in the electrical industry, which last-named materials, besides the properties mentioned above, must also have high di-electric strength, which is usually a function of the density. Any of the above types of multi-layer materials, as well as binder or book boards, used in the binding of books, and several other varieties of boards, such as counter boards, heel boards and innersole boards, used in the shoe industry, can very advantageously be made by the methods and apparatus of my invention, at very appreciable savings in labor and handling charges, by comparison with the present "wet" machine methods of producing such materials.

I claim:

1. Apparatus for the continuous production of matrix paper and similar dense multi-layer materials that have to be made from highlyhydratedvery slow" pulp stock, comprising a multiplicity of stock vat and cylinder mold units, each including a traveling endless felt on which is continuously couched a water-laden web of such stock, a pair of opposed press rolls associated with each unit and-over the lower of which the unit's individual felt is trained, said pairs of press rolls being in substantial alinement, an endless belt common to all of said units for picking up and water-impervious material, for complete and unimpaired transmission of the press roll pressure, thereby to rid the web from the first of said units of its excess water, and condition it for strong adhesion to said lower belt course, and to similarly condition each succeeding web for proper amalgamation with the accumulated webs on the under side of said lower course.

2. In apparatus for the continuous manufacture of matrix paper and similar dense multilayer products that have to be made from highlyhydrated very "slow" pulp stock, the combination with a plurality of forming cylinders for forming a plurality of wet pulp webs of said stock, a plurality of substantially alined press roll stations, one for each of said cylinders and 001m prising a pair of opposed press rolls, and a pluralcylinder to the nip of the associated pair of press rolls, of a hard-surfaced imperforate and waterimpervious traveling endless belt having its lower course trained between each pair of opposed press rolls, to provide a hard and water-impervious backing for the webs as they are passed through and pressed between said press rolls, with said belt also functioning to carry the several webs away from the press roll stations as the webs are dehydrated and amalgamated together and accumulated upon the under surface of said belt course in face-to-face relation, and means including an auxiliary roll associated with each of said felts and disposed in advance of the associated press roll station for producing contact of its conveyed wet web with either the under side of said lower belt course or the prior accumulated webs thereon.

3. In apparatus for the continuous manufacture of matrix paper and similar dense multilayer products that have to be made from highlyhydrated very "slow pulp stock, a plurality of forming cylinders for forming simultaneously and progressively a plurality of wet pulp webs of said stock, a plurality of press roll stations, one for each of said cylinders and each comprising a pair of opposed press rolls, and conveying means for transferring each wet pulp' web progressively from its forming cylinder to the nip of its associated pair of press rolls, of a hard-surfaced imperforate and water-impervious traveling endless belt having' its lower course trained between each pair of opposed press .rolls and backed up by the upper press rolls of said pairs, and means for applying the pressure of said rolls through said belt at each press roll station, to condition the first of said webs for strong adhesion to said belt course and to condition the following webs for proper amalgamation with the webs already accumulated on said belt course.

HAROLD CLEMENT FRIEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS FOREIGN PATENTS Country Date Germany Oct. 25, 1939 Germany Sept. 25,1911

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